Tag Archives: 持久连接

十一 06

Python MySQL使用持久连接

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python连接mysql中没有长连接的概念，但我们可以利用mysql的ping机制，来实现长连接功能~
思路:
1 python mysql 的cping 函数会校验连接的可用性,如果连接不可用将会产生异常
2 利用这一特性，构造一个连接丢失的循环，不断尝试连接数据库，直到连接恢复
3 使用这样的机制不需要关闭数据库功能,对于驻留进程，有大量数据进行写操作时，很有用途

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#!/usr/bin/env python  
# -*-coding:UTF-8-*-  
import sys,MySQLdb,traceback  
import time  
class mysql:  
    def __init__ (self,  
                  host   = '',  
                  user   = '',  
                  passwd = '',  
                  db     = '',  
                  port   = 3306,  
                  charset= 'utf8'  
                  ):  
        self.host   = host  
        self.user   = user  
        self.passwd = passwd  
        self.db     = db  
        self.port   = port  
        self.charset= charset  
        self.conn   = None  
        self._conn()  
 
    def _conn (self):  
        try:  
            self.conn = MySQLdb.Connection(self.host, self.user, self.passwd, self.db, self.port , self.charset)  
            return True  
        except :  
            return False  
 
    def _reConn (self,num = 28800,stime = 3): #重试连接总次数为1天,这里根据实际情况自己设置,如果服务器宕机1天都没发现就......  
        _number = 0  
        _status = True  
        while _status and _number <= num:  
            try:  
                self.conn.ping()       #cping 校验连接是否异常  
                _status = False  
            except:  
                if self._conn()==True: #重新连接,成功退出  
                    _status = False  
                    break  
                _number +=1  
                time.sleep(stime)      #连接不成功,休眠3秒钟,继续循环，知道成功或重试次数结束  
 
    def select (self, sql = ''):  
        try:  
            self._reConn()  
            self.cursor = self.conn.cursor(MySQLdb.cursors.DictCursor)  
            self.cursor.execute (sql)  
            result = self.cursor.fetchall()  
            self.cursor.close ()  
            return result  
        except MySQLdb.Error,e:  
            #print "Error %d: %s" % (e.args[0], e.args[1])  
            return False  
 
    def select_limit (self, sql ='',offset = 0, length = 20):  
        sql = '%s limit %d , %d ;' % (sql, offset, length)  
        return self.select(sql)  
 
    def query (self, sql = ''):  
        try:  
            self._reConn()  
            self.cursor = self.conn.cursor(MySQLdb.cursors.DictCursor)  
            self.cursor.execute ("set names utf8") #utf8 字符集  
            result = self.cursor.execute (sql)  
            self.conn.commit()  
            self.cursor.close ()  
            return (True,result)  
        except MySQLdb.Error, e:  
            return False  
 
    def close (self):  
        self.conn.close()  
 
if __name__=='__main__':  
    my = mysql('localhost','root','password','database',3306)  
    print my.select_limit('select * from sdb_admin_roles',1,1)  
    #my.close()